Lylose is a sweetening agent developed in the U.K. by Tate and Lyle PLC. It is approximately 0.4 the sweetness of sucrose. Because of its potential use as a sucrose substitute by individual and industrial consumers, its cariogenic potential should be determined. Initially it was compared with two concentrations of sucrose using the rat animal model and a programmed feeding regimen. Four groups (l0/group) of rats were fed the following diets: Group l -Diet NIH 2000 (56 percent sucrose); Group 2 -Diet NIH 2114 (56 percent raw corn starch); Group 3 -Basic diet NIH 2000 with Lylose (56 percent) replacing sucrose; and Group 4 -Basic diet NIH 2000 containing 28 percent sucrose and 28 percent raw corn starch. The experiment was performed using a Konig-Hofer progammable feeding machine which delivered 17 meals/17 hour period of the assigned diets. An additional 12 meals of diet 2114 was provided all four groups as a supplement. All animals were initially infected with S. mutans 67l5. Oral infection levels were determined twice weekly. After 56 experimental days the rats were sacrificed. Considering caries scores for smooth surfaces only, those animals eating lylose had scores lower than the animals consuming 56 and 28 percent sucrose (p 0.03 and 0.01 respectively). Therefore, lylose may be considered a potential substitute for sucrose.